From: Dexuan Cui decui@microsoft.com
[ Upstream commit 915cff7f38c5e4d47f187f8049245afc2cb3e503 ]
pci_restore_msi_state() directly writes the MSI/MSI-X related registers via MMIO. On a physical machine, this works perfectly; for a Linux VM running on a hypervisor, which typically enables IOMMU interrupt remapping, the hypervisor usually should trap and emulate the MMIO accesses in order to re-create the necessary interrupt remapping table entries in the IOMMU, otherwise the interrupts can not work in the VM after hibernation.
Hyper-V is different from other hypervisors in that it does not trap and emulate the MMIO accesses, and instead it uses a para-virtualized method, which requires the VM to call hv_compose_msi_msg() to notify the hypervisor of the info that would be passed to the hypervisor in the case of the trap-and-emulate method. This is not an issue to a lot of PCI device drivers, which destroy and re-create the interrupts across hibernation, so hv_compose_msi_msg() is called automatically. However, some PCI device drivers (e.g. the in-tree GPU driver nouveau and the out-of-tree Nvidia proprietary GPU driver) do not destroy and re-create MSI/MSI-X interrupts across hibernation, so hv_pci_resume() has to call hv_compose_msi_msg(), otherwise the PCI device drivers can no longer receive interrupts after the VM resumes from hibernation.
Hyper-V is also different in that chip->irq_unmask() may fail in a Linux VM running on Hyper-V (on a physical machine, chip->irq_unmask() can not fail because unmasking an MSI/MSI-X register just means an MMIO write): during hibernation, when a CPU is offlined, the kernel tries to move the interrupt to the remaining CPUs that haven't been offlined yet. In this case, hv_irq_unmask() -> hv_do_hypercall() always fails because the vmbus channel has been closed: here the early "return" in hv_irq_unmask() means the pci_msi_unmask_irq() is not called, i.e. the desc->masked remains "true", so later after hibernation, the MSI interrupt always remains masked, which is incorrect. Refer to cpu_disable_common() -> fixup_irqs() -> irq_migrate_all_off_this_cpu() -> migrate_one_irq():
static bool migrate_one_irq(struct irq_desc *desc) { ... if (maskchip && chip->irq_mask) chip->irq_mask(d); ... err = irq_do_set_affinity(d, affinity, false); ... if (maskchip && chip->irq_unmask) chip->irq_unmask(d);
Fix the issue by calling pci_msi_unmask_irq() unconditionally in hv_irq_unmask(). Also suppress the error message for hibernation because the hypercall failure during hibernation does not matter (at this time all the devices have been frozen). Note: the correct affinity info is still updated into the irqdata data structure in migrate_one_irq() -> irq_do_set_affinity() -> hv_set_affinity(), so later when the VM resumes, hv_pci_restore_msi_state() is able to correctly restore the interrupt with the correct affinity.
Link: https://lore.kernel.org/r/20201002085158.9168-1-decui@microsoft.com Fixes: ac82fc832708 ("PCI: hv: Add hibernation support") Signed-off-by: Dexuan Cui decui@microsoft.com Signed-off-by: Lorenzo Pieralisi lorenzo.pieralisi@arm.com Reviewed-by: Jake Oshins jakeo@microsoft.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/pci/controller/pci-hyperv.c | 50 +++++++++++++++++++++++++++-- 1 file changed, 47 insertions(+), 3 deletions(-)
diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c index fc4c3a15e5707..a9df492fbffa2 100644 --- a/drivers/pci/controller/pci-hyperv.c +++ b/drivers/pci/controller/pci-hyperv.c @@ -1276,11 +1276,25 @@ static void hv_irq_unmask(struct irq_data *data) exit_unlock: spin_unlock_irqrestore(&hbus->retarget_msi_interrupt_lock, flags);
- if (res) { + /* + * During hibernation, when a CPU is offlined, the kernel tries + * to move the interrupt to the remaining CPUs that haven't + * been offlined yet. In this case, the below hv_do_hypercall() + * always fails since the vmbus channel has been closed: + * refer to cpu_disable_common() -> fixup_irqs() -> + * irq_migrate_all_off_this_cpu() -> migrate_one_irq(). + * + * Suppress the error message for hibernation because the failure + * during hibernation does not matter (at this time all the devices + * have been frozen). Note: the correct affinity info is still updated + * into the irqdata data structure in migrate_one_irq() -> + * irq_do_set_affinity() -> hv_set_affinity(), so later when the VM + * resumes, hv_pci_restore_msi_state() is able to correctly restore + * the interrupt with the correct affinity. + */ + if (res && hbus->state != hv_pcibus_removing) dev_err(&hbus->hdev->device, "%s() failed: %#llx", __func__, res); - return; - }
pci_msi_unmask_irq(data); } @@ -3372,6 +3386,34 @@ static int hv_pci_suspend(struct hv_device *hdev) return 0; }
+static int hv_pci_restore_msi_msg(struct pci_dev *pdev, void *arg) +{ + struct msi_desc *entry; + struct irq_data *irq_data; + + for_each_pci_msi_entry(entry, pdev) { + irq_data = irq_get_irq_data(entry->irq); + if (WARN_ON_ONCE(!irq_data)) + return -EINVAL; + + hv_compose_msi_msg(irq_data, &entry->msg); + } + + return 0; +} + +/* + * Upon resume, pci_restore_msi_state() -> ... -> __pci_write_msi_msg() + * directly writes the MSI/MSI-X registers via MMIO, but since Hyper-V + * doesn't trap and emulate the MMIO accesses, here hv_compose_msi_msg() + * must be used to ask Hyper-V to re-create the IOMMU Interrupt Remapping + * Table entries. + */ +static void hv_pci_restore_msi_state(struct hv_pcibus_device *hbus) +{ + pci_walk_bus(hbus->pci_bus, hv_pci_restore_msi_msg, NULL); +} + static int hv_pci_resume(struct hv_device *hdev) { struct hv_pcibus_device *hbus = hv_get_drvdata(hdev); @@ -3405,6 +3447,8 @@ static int hv_pci_resume(struct hv_device *hdev)
prepopulate_bars(hbus);
+ hv_pci_restore_msi_state(hbus); + hbus->state = hv_pcibus_installed; return 0; out: